1. Field of the Invention
This invention relates to a lubricating oil additive and lubricating oils incorporating a minor proportion of said additive to depress the pour point of said oil.
The additive is a C.sub.22 -C.sub.40 branched alkyl ester based copolymer derived from an ethylenically unsaturated dicarboxylic acid material.
2. Prior Art
A wide variety of compositions comprising polymeric materials derived from the addition reaction of 1-olefins and ethylenically unsaturated carboxylic acid materials have been described in the literature as additives for fuels and lubricants. For example: U.S. Pat. No. 2,615,845 teaches that the copolymer of maleic anhydride and a straight chain 1-olefin having up to 20 carbon atoms which is subsequently esterified with long, straight chain, saturated alcohols in order to make it suitably oil-soluble can be usefully added to a mineral lubricating oil for pour point depression; and U.S. Pat. No. 2,655,479 points out that a factor of particularly great effect on the pour depressant activity of acrylic ester polymers is the length of the alkyl side chains (apparently a function of the oil solubilizing effect of the alkyl side chain) except that polymers of single esters are rarely pour point depressants; and U.S. Pat. No. 2,509,203 teaches of a pour depressant for lube oils being composed of a polymer of a di-(C.sub.10 to C.sub.16 alkyl)fumarate.
It is also known to use ester based copolymers for various other applications relating to the processing and/or utilization of petroleum products, e.g.: U.S. Pat. No. 3,449,236 teaches as a dewaxing aid, a copolymer of C.sub.6 to C.sub.28 diolefin with maleic anhydride which is then esterified or amidated with a C.sub.12 to C.sub.30 alcohol or amine; U.S. Pat. No. 4,151,069 teaches that olefin maleic anhydride copolymers esterified with C.sub.18 to C.sub.50 linear alkyl side chains are filtration aids for dewaxing of waxy lubricating oils; and copolymers of C.sub.20+ olefins with maleic anhydride with C.sub.20+ alcohols have been taught as fluidity improvers in various types of liquid hydrocarbons boiling from about 75.degree. F. to about 1,000.degree. F., including distillates, crudes and residual oils, in Dutch Application No. 69/13277.